Display panels include a number of various types of signal lines, e.g., data lines, gate lines, and touch control lines. These signal lines provide voltage signals essential to the image display function of the display panels. For example, the data lines provide data signals to the subpixels in the display panels, and the gate lines provides gate scanning signals to each row of subpixels in the display panels. When a signal line is damaged, e.g., having an open circuit, the voltage signal cannot be transmitted to the damaged signal line. As a result, the subpixels along the damaged signal line cannot receive voltage signal for image display, resulting in dark line defect. Similarly, when there is a short circuit between adjacent signal lines, e.g., a data-gate short circuit, image display defects occur.